(1) Field of the Invention
The present invention relates to a liquid crystal display and a method of manufacturing the same. More particularly, the present invention relates to a vertical alignment mode liquid crystal display and a method of manufacturing the vertical alignment mode liquid crystal display.
(2) Description of the Related Art
A liquid crystal display (“LCD”) typically includes an LCD substrate, which includes a thin film transistor (“TFT”) substrate and a cover substrate with a liquid crystal layer the interposed therebetween. The LCD displays an image by controlling a transmittance of light that passes through the liquid crystal layer. More specifically, the transmittance changes according to an alignment of liquid crystal molecules in the liquid crystal layer, which are aligned by an electric field that is generated by applying a voltage to electrodes on the TFT substrate and/or the cover substrate.
LCDs have various display modes, which are generally determined by an alignment mode of the liquid crystal molecules. For example, in a vertical alignment (“VA”) mode LCD, the liquid crystal molecules are initially aligned vertically with respect to the TFT substrate, but are aligned obliquely or horizontally to the TFT substrate when a voltage is applied to the electrodes. Specific examples of the VA mode LCD include a patterned vertical alignment (“PVA”) mode LCD and an electrically controlled birefringence (“ECB”) LCD. Although the TN, PVA and ECB mode LCDs are easy to manufacture (relative to other types of LCDs), they all have disadvantages that include, for example, a narrow viewing angle due to a vertical alignment of the liquid crystal molecules when the voltage is applied to the electrodes.
In attempts to solve the narrow viewing angle problem, additional modes have been researched, such as an in plane switching (“IPS”) mode and a plane to line switching (“PLS”) mode, for example. In the IPS mode, liquid crystal molecules are aligned along a plane by disposing two or more electrodes parallel to each other and in different layers on a substrate and inducing a horizontal electric field between the electrodes, substantially parallel to the substrate. Thus, the IPS mode LCD is a horizontal alignment (“HA”) LCD. In the PLS mode, a common electrode and pixel electrodes are disposed on a lower substrate, an insulating layer is interposed therebetween, and liquid crystal molecules move to fill a gap between an upper substrate and the lower substrate in each pixel area by forming a fringe electric field in the pixel area. Thus, in the PLS mode LCD, both vertical and horizontal electric fields are formed, as the PLS mode has a structure that forms the vertical and horizontal electric fields using the common electrode and the pixel electrodes. Since the PLS mode LCD has both vertical and horizontal electric fields, an aperture ratio and transmittance are improved.
In both the IPS and PLS modes, the electrodes are disposed on the lower substrate (which is typically the thin film transistor substrate). Therefore, a cover substrate, e.g., the upper substrate, of the IPS and PLS mode LCDs does not include electrodes. Thus, the IPS mode LCD and the PLS mode LCD both have a problem of easy generation of static electricity during a manufacturing process thereof. Moreover, an electrostatic chuck (“ESC”) cannot be used in manufacturing the IPS or PLS mode LCDs, since the cover substrate does not include an electrode, which would normally be used to generate electrostatic forces with the ESC during the manufacturing process.
In attempts to overcome the abovementioned deficiencies, it has been suggested that an electrode layer be disposed on a rear portion of the cover substrate. However, this results in defects being generated in the LCD, due to scratches made by conveyor rollers, stains and chemicals, for example.